<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        body{
            background-color:red;
            color: #fff;
            font-size: 30px;
            font-family: "Microsoft Yahei";
        }
    </style>
    <script>
        window.onload = function(){
            var oBtn = document.querySelector('#btn');
            var oDemo = document.querySelector('#demo');
            oBtn.onclick = function () {
                //这样写的问题：如果我们刷新页面，皮肤又会重置为red ---> 需要使用localStorage
                document.body.style.backgroundColor = oDemo.value;
            }
        }
    </script>
</head>
<body>
    乐淘项目 
    <select id="demo">
        <option value="red">red</option>
        <option value="yellow">yellow</option>
        <option value="blue">blue</option>
    </select>
    <input type="button" value="换肤" id="btn">
</body>
</html>